I'm going to quote from the official site:
US Social Forum, Detroit Michigan June 22-26, 2010 Downtown Detroit.
The USSF is a grassroots level "movement of movements", an open space bringing together existing efforts to create unity of thought and action across our many struggles, sectors, regions, and diverse groups. The USSF will provide a space to unite thousands - members of the local and global community, youth, retirees, the disabled, welfare recipients, organized and unorganized labor from all colors - to raise awareness about social justice, to share tactics that create social change, and to create common solutions. Together we can strategize ways to build a new United States of America for the people and by the people.

http://www.ussf2010.org/

We expect over 20,000 activists to come to Detroit in the spring. Be a part of the solution!